235
FXUS66 KEKA 042253
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
253 PM PST Thu Dec 4 2025

.SYNOPSIS...A deepen marine layer will return along the coast
tonight into Friday, with patchy drizzle. King tides combined with
surge and tidal anomaly will continue to lead in coastal flooding
in low-lying areas around Humboldt Bay on Friday. A series of
frontal system moving north of the area will bring chance of light
rain or sprinkles across the northern portion of the area Friday
and through the weekend, especially for Del Norte and Humboldt
counties.


&&

.DISCUSSION...Sunny to partly cloudy skies are observed across
Northwest California this afternoon, with generally high
temperatures in the 50s and light winds. A 1033 mb high pressure
over the Northeastern Pacific slightly "flattened" as a series of
shortwaves and associated frontal systems moves around the
northern periphery of the ridge towards the Pacific Northwest.
Blustery northerly winds are expected to developed over the
coastal headlands and exposed ridges in Humboldt and Mendocino
counties late this afternoon and evening, where gusts of 20 to 30
mph are more likely expected.

Tonight into Friday, downstream flow aloft will continue to bring
increasing cloudiness to the area as a weak cold front traverse
the Pacific Northwest. This should aid in a deep marine layer
along the North Coast. Patchy drizzle is expected to occur with
the deepening marine layer along the North Coast late tonight
through Friday morning with the saturated layer. Overnight
temperatures are forecast to run up to 5 degrees warmer compared
with Thursday`s morning. High dew points in the mid 30s to mid 40s
will preclude frost conditions across much of the interior
valleys.

Friday, another cold front approaches the area from the north.
This will bring an increasing chance of light rain or sprinkles
across Del Norte, Humboldt and Trinity counties Friday afternoon
and Friday night. Dry weather conditions are expected to prevail
in Mendocino and Lake counties. Some blustery winds will continue
over the coastal headlands and exposed ridges in Humboldt and
Mendocino counties on Friday. Lingering light showers will
continue across the northern portion of the forecast area on
Saturday.

On Sunday, another shortwave and frontal system is expected to
move north of our area. The flow aloft will become more zonal,
bringing additional chances of light rain across the northern
portion, especially for Del Norte and northern Humboldt counties.
Elsewhere, partly to mostly cloud skies are expected.

The 500 mb ridge appears to slowly build back early next through
mid next week. WPC ensemble clusters do show about an even split
(50%) of clusters that are "drier" (at least for the North Coast)
than the grand ensemble mean. The ensemble mean is by no stretch
very wet with 0.10-0.25 inches of rain in 24 hours everyday from
Monday through Wednesday, mostly for Del Norte. It could be wet
or it could be dry or both. Stay tuned. -ZVS


&&

.AVIATION...VFR conditions continue this afternoon, but a weak
system approaching the area is expected to bring lower clouds and
some possible drizzle to the coast tonight. Inland valleys are
expected to see fog again tonight, however there is some
uncertainty on how extensive this will be. For now have not added
this to the Ukiah forecast, but it is still possible it will make
its way into KUKI. Friday, the clouds are expected to push back
closer to the coast, but the may see MVFR clouds persist through the
day. -MKK


&&

.MARINE...Northerly winds remain around 15 to 20 kt this afternoon
with the strongest winds in the northern waters. Local southerly
winds have started to develop along the coast near Point Arena. late
this evening and tonight the northerly winds are expected in the to
move closer to the Mendocino coast again, but remain 15 to 20 kt
with the strongest winds in the lee of Cape Mendocino. The swell
remains fairly low, currently around 3 to 5 feet at 12 seconds and
this is generally expected to continue through Friday.

Friday afternoon and overnight a front approaching the area will
bring a short period of light southerly winds to the northern inner
waters with the outer waters turning westerly. Farther south winds
will remain northerly around 10 to 18 kt. Over the weekend winds
become southerly north of Cape Mendocino, but only around 5 to 10
kt. Farther southerly the northerly winds persist and are around 10
to 15 kt.  This pattern is expected to generally continue through
Wednesday with winds remaining fairly light as a series of weather
systems moves by to the north of the area.

Saturday a larger northwest swell builds into the waters. Currently
it looks to be around 6 to 9 feet at 10 to 12 seconds. This is
expected to diminish to around 5 to 7 feet on Sunday and generally
fluctuate around 5 to 7 feet at 12 seconds or so into early next
week. -MKK


&&

.COASTAL FLOODING...High astronomical tides are predicted to peak
on Friday. High tides are forecast to be at 8.80 feet at the North
Spit tide gauge at around 10:55 AM local time. High tides combined
with surge and tidal anomaly will result in water levels between
9.1 to 9.3 feet MLLW (Mean Low Level Water). Minor coastal
flooding around Humboldt Bay, including King Salmon and Jackson
Ranch Road in the Arcata Bottoms, will be likely between 10AM and
noon. A Coastal Flooding Advisory will be in effect from 10AM to
noon on Friday. High tides are predicted to be at 8.63 feet at
11:44 PM on Saturday. This may cause minor flooding again on
Saturday, with water level remaining nearly half of a foot above
astronomical tides inside Humboldt Bay. -ZVS


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Coastal Flood Advisory from 10 AM to noon PST Friday for
     CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 PM PST this afternoon for
     PZZ470.

     Small Craft Advisory until 2 PM PST Friday for PZZ475.

&&

$$

NOTE: The full forecast discussion is now regularly issued between
10 am/pm and 1 pm/am. Additional updates will be issued as needed.

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https://www.weather.gov/images/eka/zonemap.png